Stay on target

After nine years and more than 2,600 planet discoveries, NASA’s Kepler space telescope is entering retirement.

The spacecraft has run out of fuel needed for further operations, and will be left to float aimlessly through the cosmos in its “current, safe orbit, away from Earth.”

“As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond,” Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate, said in a statement.

When the agency first conceived of this mission 35 years ago, “we didn’t know of a single planet outside our Solar System,” according to founding principal investigator William Borucki, now retired from NASA’s Ames Research Center.

“Now that we know planets are everywhere, Kepler has set us on a new course that’s full of promise for future generations to explore our galaxy,” he added.

Artist’s conception of Kepler (via: NASA/Ames/Dan Rutter)

Launched in March 2009, the space observatory (named after astronomer Johannes Kepler) was designed to assess some 150,000 stars in the constellation Cygnus.

But it became so much more than that: The telescope took the first survey of planets in the Milky Way, and became the agency’s first mission to detect Earth-size exoplanets.

The most recent analysis of Kepler data suggests that as many as 50 percent of visible stars have small, possibly rocky planets located within their habitable zone.

“Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm,” Zurbuchen said. “Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”

Four years into the mission—after all primary objectives were met—mechanical failures temporarily halted Kepler’s observations. In 2014, NASA announced the K2 “Second Light” extension, which increased the telescope’s surveyed star count to more than 500,000.

Artist’s concept of Kepler-186f, first Earth-size planet in the habitable zone(via: NASA/Ames/JPL-Caltech/T. Pyle)

Such data has allowed scientists to better interpret stellar behavior and properties—critical to the study of stars and the planets that orbit them. Nearly a decade’s worth of disclosures has also led to improved understanding of our Milky Way and supernovae.

“We know the spacecraft’s retirement isn’t the end of Kepler’s discoveries,” according to Jessie Dotson, Kepler’s project scientist at the Ames Research Center.

In fact, scientists are expected to spend the next 10-plus years searching for new discoveries in the “treasure trove” of Kepler knowledge.

“I’m excited about the diverse discoveries that are yet to come from our data and how future missions will build upon Kepler’s results,” Dotson said.